Parcel singulation software control logic

ABSTRACT

A method and an apparatus are provided for singulating articles received in a slug and/or manipulating such articles to create a controlled gap between a trailing edge of a leading article and a leading edge of a successive article, while targeting a desired throughput. For singulation, a plurality of belts are mounted adjacent to each other with a slide chute between each pair of adjacent belts, articles moving from an infeed belt and passing from one belt to another through the chute therebetween. A plurality of sensors are positioned such that there is a single control sensor for at least selected ones of the belts, each control sensor sensing article position on a corresponding belt. Controls are provided for operating each belt in response to a corresponding control sensor, an operative state of a downstream belt and/or a difference between the desired throughput and detected throughput. For creating controlled gaps between successive articles, a plurality of belts are provided, mounted adjacent each other, articles being received on a first of the belts and passing from one belt to an adjacent belt. A plurality of control sensors are sensing article position relative to each belt and controls are provided which operate each belt in response to a corresponding control sensor, an operative state of a downstream belt and/or the difference between the desired throughput and the detected throughput. The controls are also operative to initiate stopping of a belt if a detected trailing-edge to leading-edge gap is smaller than the desired minimum gap.

This application is a Divisional of prior application Ser. No.09/716,071, filed on Nov. 17, 2000, entitled PARCEL SINGULATION SOFTWARECONTROL LOGIC and now pending.

FIELD OF INVENTION

This invention relates to article handling systems, and, moreparticularly, to a method and apparatus for singulating articles andestablishing a controlled inter-article gap.

BACKGROUND OF THE INVENTION

In mail processing, airport baggage claim service, assembly lineoperations and other applications involving transport and processing ofvarious articles, it is often necessary to separate articles randomlyreceived, sometimes enmass as a slug, stack or pile, into a stream ofsuccessive articles. This process of separating articles is generallyreferred to as “singulation”. In a post office or delivery service, forexample, packages may arrive at a conveyor system in randomly occurringslugs, the packages in each slug varying significantly in quantity, sizeand shape within allowed ranges. Singulating such packages or otherarticles is an essential preliminary step in performing sortation ormost other operations on such articles. For the articles to be sorted orotherwise processed, they also must, in most cases, be separated by agap of sufficient length. However, while at least a minimum gap betweensucceeding articles is required, spacing larger than the requiredminimum gap decreases throughput.

Automation apparatus is normally employed for article singulation andestablishing proper article separations, such prior art apparatus usingbelt and chute systems, cameras and/or arrays of photo sensors for eachbelt to determine positioning of articles on the belts, and mechanismsranging from robotic arms, to mechanical guides, to complicated controllogic for slowing down and speeding up the belts in order to separatethe articles to achieve singulation. Gapping apparatus involve varioussensors for determining existing leading-edge to leading-edge ortrailing-edge to leading-edge distance; gaps are adjusted to desiredsizes via mechanical means.

While, combined, a singulation and a gapping apparatus would accomplishthe task of singulating and gapping articles, such apparatus hasheretofore been expensive and hard to operate, requiring the use ofsophisticated technology. There exists a need for an apparatus that iscapable of achieving either one or both goals without the use ofcameras, computers to analyze digital images, or other expensiveequipment.

SUMMARY OF THE INVENTION

In accordance with the above, this invention provides a method and anapparatus for singulating articles received in a slug and/ormanipulating such articles, particularly articles of various size, tocreate a controlled gap between the trailing-edge of a leading articleand a leading-edge of a successive article. For singulation, a pluralityof belts are provided, mounted adjacent to each other, with a slidechute between each pair of adjacent belts, articles being received on afirst of the belts and passing from one belt to an adjacent belt throughthe chute therebetween. A plurality of sensors are positioned such thatthere is a single control sensor for at least selected ones of thebelts, each control sensor sensing article position relative to acorresponding belt. Controls are provided for operating each belt inresponse to a corresponding control sensor and an operative state of adownstream belt.

The control sensor may be located at an end of a corresponding belt, forexample, the exit end of the corresponding belt. The controls may beoperative to initiate stopping of a belt if a downstream belt is notrunning and a corresponding control sensor has been blocked for aconfigurable period of time. Similarly, the controls are operative tostart or re-start a belt when the downstream belt is running. Forpreferred embodiments, the configurable time period is such that thebelt has not completely stopped when a run signal is sent. Theconfigurable time period may also be adjustable to achieve a desiredapparatus throughput, such adjustment, for example, being according toan adjustment schedule. The controls may, for example, include at leastone subroutine for each belt which is run on an appropriate processor.

The invention also includes apparatus for receiving articles in a streamand creating a controlled gap between a trailing-edge of a leadingarticle and a leading-edge of a successive article. This apparatusincludes a plurality of belts mounted adjacent each other, articlesbeing received on a first of the belts and passing from one belt to anadjacent belt. A plurality of control sensors are positioned such thatthere is a single control sensor sensing article position relative toeach belt and controls are provided which operate each belt in responseto a corresponding control sensor and an operative state of a downstreambelt. The control sensor may be located at an end of a correspondingbelt, for example, the exit end of such belt.

The plurality of belts may be logically divided into a first sectionwhich minimizes a gap time and a second section which establishes atleast a minimum gap time between successive articles. The controls areoperative to initiate stopping of a belt in the first section if adownstream belt is not running and a corresponding control sensor isblocked and to send a run signal when the downstream belt is runningagain. The controls are also operative to initiate stopping of a belt inthe second section if a detected trailing-edge to leading-edge gap timeis smaller than the desired minimum gap time, and a run signal is sentto the belt after a calculated time period, the calculated time periodbeing a function of a difference between the detected gap time and theminimum gap time. More specifically, calculation of the above functionincludes: (a) setting the calculated time period to be equal to thedifference between the detected gap time and the minimum gap time if thedifference is larger than a determined fraction of the minimum gap time;and (b) setting the calculated time period to be equal to a fraction ofthe minimum gap time if the difference between the detected gap time andthe minimum gap time is smaller or equal to a determined fraction of theminimum gap time. The controls are also operative to initiate stoppingof a belt, or at least a subset of the plurality of belts, if acorresponding control sensor has been blocked for more than apredetermined time period, which time period may be adjusted to targetthe desired throughput. For some embodiments, the predetermined timeperiod is smaller than, or at most equal to a time it would take for alongest article to move past the corresponding control sensor. Thecontrols preferably consist of at least one subroutine for each belt.

The invention further includes a method usable with an apparatus formanipulating articles of various size which includes stages of beltscarrying the articles and belt controls for stopping and starting thebelts, the method maintaining a desired article throughput and includingthe steps of: (a) monitoring throughput for the article manipulation;and (b) controlling stop time intervals for at least selected ones ofthe belts to maintain the desired throughput. The step of controllingstop time intervals, step (b) above, may include: (c) adjusting at leastselected stop time intervals upward by a selected amount if currentthroughput is greater than the desired throughput; and (d) adjusting atleast selected stop time intervals downward by selected amounts ifcurrent throughput is less than the desired throughput. The stop timeintervals in steps (c) and (d) above may be adjusted according to atleast one adjustment schedule which adjustment schedule is stored in acomputer on which control subroutines are run.

The invention further includes apparatus for manipulating articles whilemaintaining a desired throughput, which apparatus includes stages ofbelts carrying the articles, and controls operating each belt, thecontrols being operative to stop and start the belts, and includingsubroutines for monitoring throughput for the article manipulation andfor controlling stop time intervals for at least selected ones of thebelts to maintain the desired throughput. The subroutines forcontrolling stop time intervals may include (a) a subroutine foradjusting at least selected intervals upward by a selected amount ifcurrent throughput is larger than the desired throughput; and (b) asubroutine for adjusting at least selected intervals downward by aselected amount if current throughput is smaller than the desiredthroughput. The adjustments by subroutines (a) and (b) above may beaccording to an adjustment schedule.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of a preferred embodiment of the invention as illustrated inthe accompanying drawings, the same reference numerals being used forcommon elements in the various figures.

Finally, the invention includes apparatus for receiving articles in aslug, singulating the articles and creating a controlled gap between atrailing-edge of a leading article and a leading-edge of a successivearticle. This apparatus includes a plurality of belts mounted adjacenteach other, articles being received on a first of the belts and passingfrom one belt to an adjacent belt. A plurality of control sensors arepositioned such that there is a single control sensor sensing articleposition relative to each belt and controls are provided which operateeach belt in response to a corresponding sensor and an operative stateof a downstream belt.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagramatic top view of a combined singulation and gappingsystem for an illustrative embodiment.

FIG. 2 is a control flow diagram for the infeed chute belt of the FIG. 1embodiment. FIG. 3 is a control flow diagram for the first belt of thesingulator section of the FIG. 1 embodiment.

FIG. 4 is a control flow diagram for the remaining belts of a singulatorsection of the FIG. 1 embodiment.

FIG. 5 is a control flow diagram for the first three belts of a gappingsection of the FIG. 1 embodiment.

FIG. 6 is a control flow diagram for the remaining belts of the gappingsection of the FIG. 1 embodiment.

FIG. 7 is a timing diagram for the last six belts of the gapping sectionof the FIG. 1 embodiment.

FIG. 8 is a timing diagram for all belts of the gapping section of theFIG. 1 embodiment illustrating minimum gap time logic.

FIG. 9 is a timing diagram for two of the belts of the gapping sectionof the FIG. 1 embodiment illustrating clump eliminator logic.

FIG. 10 is a timing schedule for changing configurable time periods.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, an illustrative apparatus in accordance with theteachings of this invention is shown for randomly receiving articles ofvariable size within selected limits in slugs having varying numbers ofarticles with varying orientations and for delivering the articles oneat a time with a controlled trailing-edge to leading-edge spacingbetween successive articles. Articles arrive and are singulated insection 40, proceed to section 42 where any remaining doubles areeliminated and large gaps between articles are reduced; and then proceedto section 44 where at least a minimum trailing-edge to leading-edgespacing between successive articles is established. Sections 42 and 44together comprise a gapping section and may also be referred to as agapping apparatus. From there, articles proceed to a sortation or otherappropriate stations for further manipulation or processing.

For the illustrative embodiment, articles arrive at singulation section40 from an infeed chute belt 60 through a large spiral slide chute 58.The singulation section is comprised of multiple belts 62 a through 62d, which are collectively referred to as surge belts 62 because theycarry forward some unsingulated slugs. Surge belts 62 are interconnectedby slide chutes 64 a-64 d, with slide chute 64 d leading to section 42.Sensors 48 a-48 d are positioned so that there is at least one sensor 48x per each surge belt 62 x. Articles proceed from the infeed chute belt60 onto the spiral slide chute 58, where they are sensed by photosensor48 a, onto a surge belt 62 a, then through slide chute 64 a, and to asurge belt 62 b, and so on: from a surge belt 62 x to a slide chute 64 xto a downstream surge belt 62(x+1). Sensors 48 x are typically locatedat the ends of the corresponding surge belts 62 x. They are preferablyplaced at the belt elevation, looking across the belt. There is beltguarding (not shown) on each side of each surge belt 62 x in order toprevent articles from falling off, holes being formed in each guardingwhere sensors 48 are located. Sensors 48 are each located within onequarter inch from a top of the corresponding belt 62 because, in theenvironment of the illustrative embodiment, articles may be as small ashalf an inch in one dimension—for example, music CDs, etc. Placingsensors 48 x at the ends of the corresponding belts 62 x means that theydetect the articles as the articles are about to move off to thecorresponding slide chute 64 x, which, combined with proper controlsettings, assists singulation while minimizing possible gaps withoutclosing them completely. Each belt is run by a motor controlled bycontrol logic. For the illustrative embodiment, surge belts 62 arelocated at ninety degree angles to each other, and slide chutes 64separating them each have a different angle and slope, with eachsuccessive slide chute 64 being narrower than the previous one. Inaddition, surge belts 62 are inclined up, with slopes rangingapproximately from thirty to forty degrees, while the slide chutes areangled down at angles which may be steeper, but extend for a shorterdistance. These inclines are not required, but further assistsingulation. Surge belts 62 are wider and longer than belts at laterstages, but each belt 62 x is narrower than the preceding belt 62(x−1),so that articles are forced into a stream.

Infeed chute belt 60 and each of the surge belts is controlled bycontrols operating each belt 62 x in response to a corresponding sensor48 x and/or an operative state for a downstream surge belt. In apreferred embodiment, the surge belts 62 run at different speeds—eachbelt is faster than the belt preceding it, which further assistssingulation because faster downstream belts carry articles away andprevent clump creation. The controls can turn each surge belt 62 on oroff, depending on its current state, the state of at least onedownstream belt, whether the corresponding sensor is sensing anyarticles, and the throughput of the whole apparatus. That is, thearticles are singulated through selective, coordinated control of the onand off states for the belts. The infeed chute belt 60 is operated by acontrol subroutine shown in FIG. 2. The surge belt 62 a is operated by acontrol subroutine shown in FIG. 3, and the remaining surge belts 62b-62 d are operated by the control subroutines shown in FIG. 4.

Section 42 consists of a set of belts 66 e-66 g, which are collectivelyreferred to as buffer belts 66 because they carry mostly singulatedarticles. Buffer belts 66 run at a faster speed than surge belts 62 insingulation section 40 and function as high speed takeaway belts. For anillustrative embodiment, belts 62 run at about 50-150 feet per minute,while belts 66 e-66 g run anywhere from 250 to 350 feet per minute. Eachbuffer belt 66 runs at a higher speed than the belt preceding it.

An article arrives at section 42 from section 40 at a buffer belt 66 eand leaves photosensor 48 e-48 g sensing articles at that belt. Eachbuffer belt 66 is operated by controls 76 according to a control flowdiagram (see FIG. 5), buffer belt 66 x being turned on or off inresponse to its current state, a corresponding sensor 48 x, the on/offstate of at least one downstream belt, for example belt 66(x+1) and, fora preferred embodiment, the throughput of the entire apparatus shown inFIG. 1.

Gapping section 44 consists of a set of belts 68 h-68 n, which arebuffer belts for an illustrative embodiment and are collectivelyreferred to as buffer belts 68. Buffer belts 68 run incrementally fasterthan each other, with speeds ranging from 200 to 500 feet per minute.Buffer belt 68h runs slower than the buffer belt 66 g. Above each belt68 x there is a corresponding photosensor 48 x. Gapping is achievedthrough controls turning each buffer belt 68 x on or off according to acontrol subroutine (FIG. 6), each buffer belt 68 x being turned on/offin response to a corresponding sensor 48 x and/or the state of at leastone downstream belt, for example belt 68(x+1). Articles arrive at thegapping section 44 from section 42 at the buffer belt 68 h and leave theapparatus at a buffer belt 68 x, for example buffer belt 68 n for theembodiment of FIG. 1, from where they proceed to their next destination,for example a sortation station.

Additional fail-safes are available in the apparatus. Above surge belts62, buffer belts 66 and buffer belts 68, additional photosensors 46 arelocated (shown for the surge belt 62 d; not shown, but present aboveother belts 62, 66 and 68). These photosensors are generally fordetection of jams that cannot be solved through cycling belts on and offand require human intervention. When articles exit at buffer belt 68 n,any remaining doubled articles, which should be minimal, if any, aredetected and re-routed back to the infeed chute 60 through a return path(not shown), so that they will go through the singulation process again.Belt controls 76 are implemented using a control computer capable ofconcurrently executing several subroutines, inputs to which are thestates of sensors and belts, as described below, and outputs from whichcontrol motors (not shown) for each of the belts in the apparatus. Thesubroutines may be implemented in any computer language, and may consistof additional subroutines.

Although the preferred embodiment uses a single computer to execute allsubroutines that comprise controls 76 in parallel, alternativeembodiments may use a separate computer for each set of subroutines orbypass software and implement the subroutines in hardware or hybridcircuits. A number of the subroutines at some point refer to aconfigurable time 5 period, which is a variable setting, configuredaccording to a table in FIG. 10. An additional feedback loop (notshown)continuously monitors the apparatus output through athroughput-monitoring subroutine and, based upon a target throughput,adjusts variable time parameters to speed up or slow down the apparatusthrough changing the configurable time periods.

FIG. 2 is a flow diagram of an illustrative control subroutine foroperating the infeed chute belt 60 (FIG. 1) A default state for thissubroutine is state-80, system on, no faults, where the infeed belt isturned on and is running. When the system is in this state, thesubroutine monitors a photosensor 48 a and continuously runs a query 82to see if the photosensor 48 a has been blocked for more than aconfigurable time period 89 (FIG. 10). If an answer to this query isnegative, the system proceeds as previously, running the belt in step 85and returning to state 80. If, however, photosensor 48 a has beenblocked for a time greater than the configurable time 89, it means thatseveral articles are passing together, which is undesirable. In thatcase, the motor for the infeed belt is turned off (step 84) to delaytrailing articles, which are still on the infeed chute belt 60 and toallow articles which are already on the surge belt 62 a to proceed. Whenthe infeed chute belt is stopped, a query 86 is continuously run tocheck if the photosensor 48 a is still blocked (i.e. if articlesblocking the sensor have cleared). If the sensor is clear, thesubroutine returns to query 82 to determine whether to restart theinfeed chute belt 60. In this way, the control subroutine beginssingulation by separating the slug of articles into separate articles orsmall clumps of articles. The singulation process continues withcontrol! subroutines shown in FIGS. 3 and 4.

FIG. 3 is a flow diagram of a control subroutine for the surge belt 62a. A default state for this subroutine is state 90—system on, no faults,where the surge belt 62 a is running. While the system is in this state,a query 92 is continuously run to check if the downstream belt—surgebelt 62 b—is turned on. If the downstream belt is stopped, a query 93 isrun to check if a photosensor 48(a−1) is indicating an article at thebeginning of the surge belt 62 b. If the photosensor 48(a−1) isindicating an article and the downstream belt is not running, surge belt62 a needs to be stopped (step 94) in order to avoid creating moredoubles by bumping articles that are currently on the surge belt 62 ainto those that are currently on the surge belt 62 b. If, however, thereare no articles at the beginning of the downstream belt, then it is safeto continue running surge belt 62 a (step 96) and system returns to thedefault state 90.

If the query 92 indicates that downstream belt 62 b is running, a query95 is run to check if the photosensor 48(a−1) has been blocked for aperiod longer than a configurable time period 99 (FIG. 10). If theanswer is negative, belt 62 a continues to run (step 96) and systemreturns to default state 90. A positive answer to query 95 is a signthat an article double is coming through which needs to be singulated.In order to achieve singulation, surge belt 62 a is stopped (step 97) toallow surge belt 62 b to take away a front article of the double. Oncethe surge belt 62 a is stopped, a query 98 is continuously run to checkif the photosensor 48(a−1) has cleared. When photosensor 48(a−1)indicates that there are no articles present at the beginning of belt 62b, the system proceeds to run query 92 and repeats the steps thereafteras indicated above. This subroutine thus creates gaps between at leastsome consecutive articles by not running the belt 62 a when photosensor48(a−1) indicates that there are articles at the beginning of thedownstream belt, but running belt 62 a when this condition does notexist. This subroutine does not attempt to properly size or minimizesuch gaps, leaving that for the later stages 42 and 44.

FIG. 4 is a flow diagram of a control subroutine for operating belts 62b, 62 c and 62 d. For each of those surge belts, referred to as surgebelt 62 x, a separate instance of the subroutine is run. A default statefor this subroutine is state 100, where surge belt 62 x is running andthere are no faults. When the system is in state 100, a query 102 iscontinuously run to check if downstream surge belt 62(x+1) is running.If the answer query 102 is negative the downstream belt is not running aquery 103 is run to check if a photosensor 48 x is indicating presenceof an article. If no article is detected, the subrouting continuesrunning belt 62 x (step 104) and returns to the default state 100. If,however, an article is detected, belt 62 x is stopped (step 105) toavoid creating new doubles, and the subroutine returns to query 102. Ifthe answer to query 102 is positive (i.e. the downstream belt isrunning), a query 106 is run to check whether the photosensor 48 x hasbeen blocked for a period of time longer than a configurable time period107 (FIG. 10). A positive answer to the query 106 indicates that thereis still an article double, and surge belt 62 x is turned off for aconfigurable time period 109(FIG. 10) to facilitate separation of thedouble, and then turned back on, with the system returning to defaultstate 100. The fact that the downstream belt 62 x is running issufficient to assure that a gap is created during the stopping for theconfigurable time period 109. A negative answer to the query 106indicates that there is no double currently passing through belt 62 x,surge belt 62 x thus continuing to run (step 104) and the subroutinereturning to default state 100.

FIG. 5 is a diagram of control subroutine for controlling each of thebuffer belts 66 e-66 g in the section 42. Belts 66 x are high speedtakeaway belts and the main goal for this section is to minimize gapsbetween the articles, so that the next section 44 can increase them tothe desired minimum size. For each of the buffer belts 66 x, a separateinstance of the subroutine is run. A default state for this subroutineis state 110—system on, no faults—where a belt 66 x is running. When thesubroutine is in this state, a query 112 is continuously run to check ifthe downstream belt 66(x+1) is running. If the downstream belt isrunning, there is no danger of creating additional doubles; thesubroutine therefore permits belt 66 x to continue running (step 113)and returns to default state 110.

If the downstream belt is not running, a query 114 is run to check ifphotosensor 48 x is indicating the presence of an article at the end ofthe belt 66 x. If there is an article, buffer belt 66 x is stopped (step115) and the subroutine returns to query 112. If there is no articlepresent, the subroutine continues to run buffer belt 66 x (step 113),returning to the default state 110 despite the fact that downstream belt66(x+1) is not running. This is done in order to minimize the gapbetween the articles; no additional doubles will be created, because, bythe time the next article moves to the end of buffer belt 66 x, eitherthe downstream belt will be running, or both queries 112 and 114 willreturn negative results and belt 66 x will be stopped, avoidingcombining two articles into a double.

FIG. 6 is a flow diagram of a control subroutine responsible foroperation of belts 68 in the section 44. The main goal for this sectionis to establish at least a minimum required gap between each pair ofsuccessive articles. In order to do that, gap time is increased to atleast minimum gap time in all cases where a detected gap is not longenough. A separate instance of the subroutine is run for each bufferbelt 68 x. A default state for this subroutine is state 120—system on,no faults, where belt 68 x is running. When the subroutine is in thatstate, a query 122 is continuously run to check if the trailing-edge toleading-edge gap for successive articles passing sensor 48 x is largerthan a required minimum gap 127 (see FIG. 7a). The check is madeaccording to the timing principles described later in conjunction withFIGS. 7-9. A negative answer to query 122 indicates that the detectedgap is not of sufficient duration, and buffer belt 68 x is stopped for atime period 129 described to be in conjunction with FIGS. 7-9 (step128). After the belt has been stopped for the time period 129, thesubroutine returns to query 122. However, if during the time period 129when buffer belt 68 x was stopped, downstream buffer belt 68(x+1) wasalso not running, the detected gap was not increased or increased by aninsufficient amount. The illustrative apparatus includes seven bufferbelts 68 running at different speeds, which increases the probabilitythat, if the detected gap is not sufficient, the downstream belt 68(x+1)will be running during the whole time period 129, thus creating at leastthe minimum required gap.

A positive answer to query 122 indicates that the detected gap is ofsufficient duration. Query 123 is then made to determine if downstreambelt 68(x+1) is running. If an answer is positive, there is no danger ofdecreasing the detected gap, and the subroutine proceeds to run belt 68x (step 124), returning to default state 120. If, however, thedownstream belt is not running, a query 125 is run to determine ifphotosensor 48 x indicates the presence of an article at the end of belt68 x. If there is no article present, the subroutine continues runningbuffer belt 68 x and returns to query 122, which monitors the detectedgap. If photosensor 48 x is not clear—the article is present—thesubroutine sends a stop signal to a motor for belt 68 x (step 126) andreturns to query 122, which ensures that the detected gap is not reducedbelow the minimum required gap.

FIGS. 7a and 7 b are timing diagrams that further illustrate behavior ofqueries 122 and 128 (FIG. 6). FIG. 7a shows how the existingtrailing-edge to leading-edge gap is detected. Sensor 48 x is “on” whenthere is no article passing, and “off” when there is an article at theend of the belt 68 x (FIG. 1). If the minimum gap time 127 is shorterthan detected gap time 131 and both belts 68 x and 68(x+1) are on, thenthe query 122 returns “yes”, the query 123 (FIG. 6) returns “yes” andbelt 68 x continues to run.

FIG. 7b illustrates behavior according to the control flow diagram ofFIG. 6 when the detected gap time 131 is shorter than the minimumrequired gap time, as indicated by sensor 48 x. In that case, a “stop”signal is sent to belt 68 x in order to increase the gap. After acalculated period of time 132 (shown in FIG. 8), a “run” signal is sentto belt 68 x, restarting the belt.

When the “stop” signal is sent, belt 68 x does not stop immediately—asevery mechanical element, it has inertia and requires some time to slowdown and stop. Since the electronics are thus faster than the mechanicalparts, the stop period needs to be lengthened to take this differenceinto account. A timing diagram for determination of the calculated timeperiod 132 is shown in FIG. 8. If a difference between the detected gaptime and the minimum required gap time is less than one third of theminimum required gap time, the calculated stop period is set to be onehalf of the minimum required gap time. This is done in order to slowdown the belts enough to create at least a minimum required gap. Forexample, if the minimum gap between trailing and leading of successivearticles is T, and the detected gap is 4T/5, the calculated stop period132 is set to T/2. The appropriate times T are calculated based on beltspeeds, application, field-testing results, etc. If the differencebetween the detected gap time and the minimum required gap time is equalto or greater than one third of the minimum required gap time, thecalculated stop time period is set to be the difference between thedetected gap time and the minimum gap time.

FIG. 9 illustrates timing logic employed in a subset of belts 68 x (inthe illustrative embodiment this subset consists of belts 68 m and 68 k)that facilitates eliminating doubles that were not eliminated in theprevious stages, where a double is a set of articles following soclosely one after another that there is no gap to detect. In order tocreate gaps between the articles in the doubles, additional “clumpeliminator” logic is employed. According to this timing logic, if sensor48 x is off for longer than a preset time period 134, belt 68 x isturned off for a configurable time period 133 in order to allow a frontarticle in the double to pass in order to create a gap. The preset timeperiod 134 is generally set to equal to or less than an approximate timeit would take for a largest article to pass (in the illustrativeembodiment, the length of the largest possible article is known).

FIG. 10 is an illustrative timing schedule for changing the configurabletime periods discussed in conjunction with FIGS. 2, 3 and 4. At anygiven time, all configurable time periods are set to be equal to thevalues in one of the columns of FIG. 10. For example, column 140 bindicates that the configurable time period 89 for the infeed chute belt60 should be set to 1 second, a configurable time period 99 for the belt62 a should be set to 0.5 seconds, a configurable time period 107 forthe belt 62 b on-time should be set to 0.31 seconds, and a configurabletime period 109 for the belt 62 b off-time should be set to 0.57seconds. When the throughput-monitoring subroutine indicates that thedetected throughput differs from a desired throughput, the configurabletime periods are adjusted by changing all values to those in an adjacentcolumn. When the detected throughput is greater than the targetthroughput, a left column is picked, and when the current throughput isless than the desired throughput, a right column is picked. Theconfigurable time periods are thus adjusted to target the desiredthroughput. Although in the illustrative embodiment the timing scheduleof FIG. 10 is used to determine the configurable time periods, dependingon application and other factors, algorithms, different timing schedulesor other techniques may be utilized to calculate configurable timeperiods to achieve the desired throughput. In addition, configurabletime periods may be adjusted based on feedback from apparatus locatedafter the apparatus of the FIG. 1 illustrative embodiment. For example,the required minimum gap time period may be dynamically adjusted, basedon selected factors both from the present apparatus and from otherapparatus used with it, such as size of the articles, desiredthroughput, accuracy of processing at the downstream stations, etc.

Although the illustrative embodiment of the invention has been shown inthe accompanying drawings and described in the Detailed Description, itwill be understood that the invention is not limited to the embodimentdisclosed. The number and kinds of belts employed, slide chute anglesand sizes, as well as positioning of sensors and the correspondingcontrol subroutines can each be modified. The present invention iscapable of rearrangements and modifications of parts and elements by oneskilled in the art without departing from the spirit and scope of theinvention, which is to be defined only by the appended claims.

What is claimed is:
 1. An apparatus for manipulating articles,comprising: a conveyor configured and arranged to convey articles alonga path; a sensor that detects the presence of articles at a particularlocation along the path; and at least one controller operatively coupledto the sensor and configured to determine whether the sensor hascontinuously detected the presence of at least one article at theparticular location for an elapsed time period that is greater than athreshold time period, wherein the at least one controller is furtherconfigured and arranged to receive a signal indicative of a measuredoperational state of the apparatus, and to adjust the threshold timeperiod in response to the signal.
 2. The apparatus of claim 1, whereinthe conveyor comprises at least first and second belts arranged suchthat articles received on the first belt pass to the second belt tothereby travel along the path.
 3. The apparatus of claim 2, wherein theat least one controller is further configured such that, at least undercertain circumstances, the at least one controller alters an operationalparameter of the first belt in response to determining that the sensorhas continuously detected the presence of at least one article at theparticular location for an elapsed time period that is greater than thethreshold time period.
 4. The apparatus of claim 3, wherein the at leastone controller is further configured such that, if the first belt isrunning, the at least one controller alters the operational parameter ofthe first belt in response to determining that the elapsed time periodhas exceeded the threshold time period.
 5. The apparatus of claim 4,wherein the at least one controller is further configured such that, ifthe first belt is running, the at least one controller initiatesstopping of the first belt in response to determining that the elapsedtime period has exceeded the threshold time period.
 6. The apparatus ofany of claim 5, wherein the at least one controller is furtherconfigured such that, if the first belt is not running, the at least onecontroller initiates starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.7. The apparatus of claim 3, wherein the at least one controller isfurther configured such that, if the first and second belts are running,the at least one controller alters the operational parameter of thefirst belt in response to determining that the elapsed time period hasexceeded the threshold time period.
 8. The apparatus of claim 3, whereinthe at least one controller is further configured such that, if thefirst and second belts are running, the at least one controllerinitiates stopping of the first belt in response to determining that theelapsed time period has exceeded the threshold time period.
 9. Theapparatus of claim 8, wherein the at least one controller is furtherconfigured such that, if the first belt is not running and the secondbelt is running, the at least one controller initiates starting of thefirst belt if the sensor does not detect the presence of at least onearticle at the particular location.
 10. The apparatus of claim 9,wherein the at least one controller is further configured such that, ifthe first belt is running and the second belt is not running, the atleast one controller initiates stopping of the first belt if the sensordetects the presence of at least one article at the particular location.11. The apparatus of claim 8, wherein the at least one controller isfurther configured such that, if the first belt is running and thesecond belt is not running, the at least one controller initiatesstopping of the first belt if the sensor detects the presence of atleast one article at the particular location.
 12. The apparatus of claim8, wherein the at least one controller is further configured such that,if the first and second belts are not running, the at least onecontroller initiates starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.13. The apparatus of claim 9, wherein the at least one controller isfurther configured such that, if the first and second belts are notrunning, the at least one controller initiates starting of the firstbelt if the sensor does not detect the presence of at least one articleat the particular location.
 14. The apparatus of claim 10, wherein theat least one controller is further configured such that, if the firstand second belts are not running, the at least one controller initiatesstarting of the first belt if the sensor does not detect the presence ofat least one article at the particular location.
 15. The apparatus ofclaim 11, wherein the at least one controller is further configured suchthat, if the first and second belts are not running, the at least onecontroller initiates starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.16. The apparatus of claim 3, wherein the at least one controller isfurther configured such that, if the first and second belts are running,the at least one controller initiates stopping of the first belt for apredetermined time period in response to determining that the elapsedtime period has exceeded the threshold time period, the at least onecontroller further being configured to initiate starting of the firstbelt after the predetermined time period has elapsed.
 17. The apparatusof claim 16, wherein the predetermined time period is such that thefirst belt has not completely stopped when the at least one controllerinitiates starting of the first belt after the predetermined time periodhas elapsed.
 18. The apparatus of claim 16, wherein the at least onecontroller is further configured to adjust the predetermined time periodin response to a measured throughput of the apparatus.
 19. The apparatusof claim 16, wherein the predetermined time period is adjustable toachieve a desired apparatus throughput.
 20. The apparatus of claim 16,wherein the at least one controller is further configured to adjust thepredetermined time period according to an adjustment schedule.
 21. Theapparatus of claim 16, wherein the at least one controller is furtherconfigured such that, if the first and second belts are not running, theat least one controller initiates starting of the first belt if thesensor does not detect the presence of at least one article at theparticular location.
 22. The apparatus of claim 21, wherein the at leastone controller is further configured such that, if the first belt isrunning and the second belt is not running, the at least one controllerinitiates stopping of the first belt if the sensor detects the presenceof at least one article at the particular location.
 23. The apparatus ofclaim 16, wherein the at least one controller is further configured suchthat, if the first belt is running and the second belt is not running,the at least one controller initiates stopping of the first belt if thesensor detects the presence of at least one article at the particularlocation.
 24. The apparatus of claim 3, wherein the sensor is located atan end of the first belt.
 25. The apparatus of claim 24, wherein the endis an exit end of the first belt.
 26. The apparatus of claim 1, whereinthe at least one controller is further configured to adjust thethreshold time period according to an adjustment schedule.
 27. Theapparatus of claim 3, wherein the threshold time period is less than orequal to a time it would take for a longest article to travel past thesensor.
 28. The apparatus of claim 2, further comprising a slide chutedisposed between the first and second belts so as to form a part of thepath defined by the at least first and second belts.
 29. The apparatusof claim 3, further comprising a slide chute disposed between the firstand second belts so as to form a part of the path defined by the atleast first and second belts.
 30. The apparatus of claim 1, wherein themeasured operational state of the apparatus comprises a measuredthroughput of the apparatus.
 31. In an apparatus for manipulatingarticles comprising a conveyor configured and arranged to conveyarticles along a path, and a sensor that detects the presence ofarticles at a particular location along the path, a method comprising astep of: (a) determining whether the sensor has continuously detectedthe presence of at least one article at the particular location for anelapsed time period that is greater than a threshold time period; and(b) measuring an operational state of the apparatus; and (c) adjustingthe threshold time period based upon the measured operational state ofthe apparatus.
 32. The method of claim 31, wherein the conveyorcomprises at least first and second belts arranged such that articlesreceived on the first belt pass to the second belt to thereby travelalong the path.
 33. The method of claim 32, further comprising a stepof: (d) at least under certain circumstances, altering an operationalparameter of the first belt in response to determining that the sensorhas continuously detected the presence of at least one article at theparticular location for an elapsed time period that is greater than thethreshold time period.
 34. The method of claim 33, wherein the step (d)includes: if the first belt is running, altering the operationalparameter of the first belt in response to determining that the elapsedtime period has exceeded the threshold time period.
 35. The method ofclaim 34, wherein the step (d) includes: if the first belt is running,initiating stopping of the first belt in response to determining thatthe elapsed time period has exceeded the threshold time period.
 36. Themethod of any of claim 35, wherein the step (d) includes: if the firstbelt is not running, initiating starting of the first belt if the sensordoes not detect the presence of at least one article at the particularlocation.
 37. The method of claim 33, wherein the step (d) includes: ifthe first and second belts are running, altering the operationalparameter of the first belt in response to determining that the elapsedtime period has exceeded the threshold time period.
 38. The method ofclaim 33, wherein the step (d) includes: if the first and second beltsare running, initiating stopping of the first belt in response todetermining that the elapsed time period has exceeded the threshold timeperiod.
 39. The method of claim 38, wherein the step (d) includes: ifthe first belt is not running and the second belt is running, initiatingstarting of the first belt if the sensor does not detect the presence ofat least one article at the particular location.
 40. The method of claim39, wherein the step (d) includes: if the first belt is running and thesecond belt is not running, initiating stopping of the first belt if thesensor detects the presence of at least one article at the particularlocation.
 41. The method of claim 38, wherein the step (d) includes: ifthe first belt is running and the second belt is not running, initiatingstopping of the first belt if the sensor detects the presence of atleast one article at the particular location.
 42. The method of claim38, wherein the step (d) includes: if the first and second belts are notrunning, initiating starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.43. The method of claim 39, wherein the step (d) includes: if the firstand second belts are not running, initiating starting of the first beltif the sensor does not detect the presence of at least one article atthe particular location.
 44. The method of claim 40, wherein the step(d) includes: if the first and second belts are not running, initiatingstarting of the first belt if the sensor does not detect the presence ofat least one article at the particular location.
 45. The method of claim41, wherein the step (d) includes: if the first and second belts are notrunning, initiating starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.46. The method of claim 33, wherein the step (d) includes: if the firstand second belts are running, initiating stopping of the first belt fora predetermined time period in response to determining that the elapsedtime period has exceeded the threshold time period, and initiatingstarting of the first belt after the predetermined time period haselapsed.
 47. The method of claim 46, wherein the predetermined timeperiod is such that the first belt has not completely stopped when asignal is sent to initiate starting of the first belt after thepredetermined time period has elapsed.
 48. The method of claim 46,further comprising a step of: (e) adjusting the predetermined timeperiod according to an adjustment schedule.
 49. The method of claim 46,wherein the step (d) includes: if the first and second belts are notrunning, initiating starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.50. The method of claim 49, wherein the step (d) includes: if the firstbelt is running and the second belt is not running, initiating stoppingof the first belt if the sensor detects the presence of at least onearticle at the particular location.
 51. The method of claim 46, whereinthe step (d) includes: if the first belt is running and the second beltis not running, initiating stopping of the first belt if the sensordetects the presence of at least one article at the particular location.52. The method of claim 33, wherein the sensor is located at an end ofthe first belt.
 53. The method of claim 52, wherein the end is an exitend of the first belt.
 54. The method of claim 31, wherein the step (c)comprises adjusting the threshold time period according to an adjustmentschedule.
 55. A computer-readable medium for use with a processorincluded in an apparatus for manipulating articles, the apparatusincluding a conveyor configured and arranged to convey articles along apath, and a sensor that detects the presence of articles at a particularlocation along the path, the computer-readable medium having a pluralityof instructions stored thereon, which, when executed by the processor,cause the processor to perform a step of: (a) determining whether thesensor has continuously detected the presence of at least one article atthe particular location for an elapsed time period that is greater thana threshold time period; and (b) adjusting the threshold time period inresponse to receiving a signal indicative of a measured operationalstate of the apparatus.
 56. The computer-readable medium of claim 55,wherein the conveyor comprises at least first and second belts arrangedsuch that articles received on the first belt pass to the second belt tothereby travel along the path.
 57. The computer-readable medium of claim56, wherein the computer-readable medium has further instructions storedthereon, which, when executed by the processor, cause the processor toperform the further step of: (c) at least under certain circumstances,altering an operational parameter of the first belt in response todetermining that the sensor has continuously detected the presence of atleast one article at the particular location for an elapsed time periodthat is greater than the threshold time period.
 58. Thecomputer-readable medium of claim 57, wherein the step (c) includes: ifthe first belt is running, altering the operational parameter of thefirst belt in response to determining that the elapsed time period hasexceeded the threshold time period.
 59. The computer-readable medium ofclaim 58, wherein the step (c) includes: if the first belt is running,initiating stopping of the first belt in response to determining thatthe elapsed time period has exceeded the threshold time period.
 60. Thecomputer-readable medium of any of claim 59, wherein the step (c)includes: if the first belt is not running, initiating starting of thefirst belt if the sensor does not detect the presence of at least onearticle at the particular location.
 61. The computer-readable medium ofclaim 57, wherein the step (c) includes: if the first and second beltsare running, altering the operational parameter of the first belt inresponse to determining that the elapsed time period has exceeded thethreshold time period.
 62. The computer-readable medium of claim 57,wherein the step (c) includes: if the first and second belts arerunning, initiating stopping of the first belt in response todetermining that the elapsed time period has exceeded the threshold timeperiod.
 63. The computer-readable medium of claim 62, wherein the step(c) includes: if the first belt is not running and the second belt isrunning, initiating starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.64. The computer-readable medium of claim 63, wherein the step (c)includes: if the first belt is running and the second belt is notrunning, initiating stopping of the first belt if the sensor detects thepresence of at least one article at the particular location.
 65. Thecomputer-readable medium of claim 62, wherein the step (c) includes: ifthe first belt is running and the second belt is not running, initiatingstopping of the first belt if the sensor detects the presence of atleast one article at the particular location.
 66. The computer-readablemedium of claim 62, wherein the step (c) includes: if the first andsecond belts are not running, initiating starting of the first belt ifthe sensor does not detect the presence of at least one article at theparticular location.
 67. The computer-readable medium of claim 63,wherein the step (c) includes: if the first and second belts are notrunning, initiating starting of the first belt if the sensor does notdetect the presence of at least one article at the particular location.68. The computer-readable medium of claim 64, wherein the step (c)includes: if the first and second belts are not running, initiatingstarting of the first belt if the sensor does not detect the presence ofat least one article at the particular location.
 69. Thecomputer-readable medium of claim 65, wherein the step (c) includes: ifthe first and second belts are not running, initiating starting of thefirst belt if the sensor does not detect the presence of at least onearticle at the particular location.
 70. The computer-readable medium ofclaim 57, wherein the step (c) includes: if the first and second beltsare running, initiating stopping of the first belt for a predeterminedtime period in response to determining that the elapsed time period hasexceeded the threshold time period, and initiating starting of the firstbelt after the predetermined time period has elapsed.
 71. Thecomputer-readable medium of claim 70, wherein the predetermined timeperiod is such that the first belt has not completely stopped when asignal is sent to initiate starting of the first belt after thepredetermined time period has elapsed.
 72. The computer-readable mediumof claim 70, wherein the computer-readable medium has furtherinstructions stored thereon, which, when executed by the processor,cause the processor to perform the further step of: (c)-adjusting thepredetermined time period according to an adjustment schedule.
 73. Thecomputer-readable medium of claim 70, wherein the step (c) includes: ifthe first and second belts are not running, initiating starting of thefirst belt if the sensor does not detect the presence of at least onearticle at the particular location.
 74. The computer-readable medium ofclaim 73, wherein the step (c) includes: if the first belt is runningand the second belt is not running, initiating stopping of the firstbelt if the sensor detects the presence of at least one article at theparticular location.
 75. The computer-readable medium of claim 70,wherein the step (c) includes: if the first belt is running and thesecond belt is not running, initiating stopping of the first belt if thesensor detects the presence of at least one article at the particularlocation.
 76. The computer-readable medium of claim 55, wherein the step(c) comprises adjusting the threshold time period according to anadjustment schedule.
 77. The apparatus of claim 30, wherein the at leastone controller is configured to adjust the threshold time perioddownward if the measured throughput is greater than a desiredthroughput, and to the threshold time period upward if the measuredthroughput is lower than the desired throughput.
 78. The method of claim54, wherein the step (c) comprises: adjusting the threshold time perioddownward if the measured throughput is greater than a desiredthroughput, and adjusting the threshold time period upward if themeasured throughput is lower than the desired throughput.
 79. Thecomputer-readable medium of claim 55, wherein the measured operationalstate of the apparatus comprises a measured throughput of the apparatus.80. The method of claim 31, wherein the measured operational state ofthe apparatus comprises a measured throughput of the apparatus.
 81. Thecomputerreadable medium of claim 79, where the step (b) comprises:adjusting the threshold time period downward if the measured throughputos greater than a desired throughput, and adjusting the threshold timeperiod upward if the measured troughput is lower than the desiredthroughput.